Assembly method for beam structures

ABSTRACT

A beam structure for a viaduct is disclosed in which hollow beams of reinforced concrete are joined in end to end relationship. The end portion of each beam has an internally extending flange in which the reinforcing members of the beam are anchored. Adjacent beams are inter-connected by reinforcing cables extending across the join and embedded in the adjacent flanges of the beams. The reinforcing cables and members together act to place each flange under compression. A hardenable mass injected between adjacent beams is also placed under compression by the reinforcing cables joining the two beams and provides a continuous beam structure.

United States Patent Macchi 1 1 Jan. 29, 1974 [541 ASSEMBLY METHOD FOR BEAM 3,230,683 1/1966 Foster .7. 52/584 X STRUCTURES 3,528,208 9/ I 970 1 1 3,570,207 33/1971 Inventor: Romualdo Macchi, Via S Paolo 3,645,056 2/1972 Gerola 52/259 Pisa, Italy '7 Primary Examiner-Price C. Faw, Jr. [b2] Bled July 1972 Attorney, Agent, or Firm-John J. McGlew et a1. [21] Appl. No.: 276,022

[57] ABSTRACT [30] Foreign Application Priority D t A beam structure for a viaduct is disclosed in which hollow beams of reinforced concrete are joined in end Aug. 2, 1971 Italy 9633 71 to and relationship. The end portion of each beam has 52 U.S. C1 52/741, 52/227, 52/259 an internally extending flange in which h reihfmhg 51 Int. Cl. E04C 3/26 members the beam are Adlaheht beams [58] Field of Search 52/741, 745 744 726, 223 R, are inter-connected by reinforcing cables extending 52/259, 227, 229, 584 396; 264/34 across the join and embedded in the adjacent flanges of the beams. The reinforcing cables and members to-' [56] References Cited gether act to place each flange under compression. A UNITED STATES PATENTS hardenable mass injected between adjacent beams is also placed under compression by the reinforcing ca- 1,964,131 6/1934 Nelson et a1 52/396 bles joining the two beams and provides a continuous 2,184,137 12/1939 Brewer 52/396 X beam structure 2,685,194 8/1954 Amirikian 52/229 X 3,070,845 1/1963 Cheskin 52/223 R 10 Claims, 12 Drawing Figures 1 ASSEMBLY METHOD FOR BEAM STRUCTURES The present invention relates to beam structures for use in bridges and viaducts for example.

The invention provides a beam structure, for bridges and viaducts, and like structures, comprising a plurality of beams of prestressed reinforced concrete lying in end to end relationship, and a rigid junction between each pair of adjacent end portions of the beams to make the structure continuous.

The invention further provides a beam structure, comprising two beams lying in end to end relationship each beam having elongate reinforcing members extending under tension between opposite end portions, and reinforcing means coupling the adjacent end portions of the two beams under tension, the reinforcing members and reinforcing means in each said adjacent end portion overlapping one another and being anchored at axially spaced locations in the end portion to place under compression that portion of the beam lying between the anchorings.

The invention yet further provides a method of erecting a continuous beam structure, comprising the steps of placing at least two beams in end to end relationship, securing the adjacent end portions of the two beams together with reinforcing means, injecting a hardenable mass between the adjacent end portions of the two beams and tensioning the reinforcing means to place the hardened mass under a compressive stress.

Beam structures embodying the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which:

FIG. 1 is a fragmentary longitudinal section of a beam structure, the section being taken on the line II of FIG. 2;

FIG. 2 is a fragmentary longitudinal section taken on the line II-II of FIG. 1;

FIG. 3 is a fragmentary cross-section taken on the line III-III of FIG. 1;'

FIG. 4 is a detail of FIG. 2 to an enlarged scale;

FIGS. 5 and 6 are fragmentary side elevations of a viaduct structure respectively during and after its erection;

FIGS. 7 and 8 are fragmentary side elevations of another viaduct structure respectively during and after its erection;

FIG. 9 is a fragmentary side elevation indicating one form of junction between two beams;

FIG. 10 is a fragmentary side elevation indicating another form of junction between two beams.

FIG. 11 illustrates zones between adjacent beams into which a hardenable mass can be injected.

FIG. 12 is a side elevation of the viaduct of FIGS. 7 and 8 illustrating how a beam is fitted into position.

As shown in FIGS. 1 to 4, two beams 1 and 3 are coupled in end to end relationship. The end portion of the beam 3 has a step 3A which supports a step 1A of complementary shape in the adjacent end portion of the beam 1. The end faces of the adjacent end portions of the beams define a gap to allow a limited amount of relative longitudinal movement between the beams while the two steps 1A, 3A are in intimate contact with one another. The two beams are prefabricated and each has a hollow, that is an annular, cross-section (see FIG. 3) with laterally extending flanges 3B, 3C as for a viaduct. The flanges 3B and 3C are arranged so that they can be continuously joined to parallel beams of similar strucflanges 9 and ture extending along opposite sides of the beam 3. The internal cavity of each beam enables the two beams l and 3 to be readily anchored in end to end relationship.

Each beam is provided with a plurality of precompression cables. In the beam 1 a plurality of cables 5 extending the length of the beam 1 are anchored at opposite ends to corresponding opposite end portions or heads of the beam 1. In the beam 3 a plurality of cables 7 extending the length of the beam 3 are anchored at opposite ends to corresponding opposite end portions or heads of the beam 3.

Each end portion of each beam is provided with a relatively thick internally extending flange, the dimension of the flange in the axial direction of the structure beinggreater than that in the transverse dimension. The end flange 9 of the beam 1 lies adjacent the end flange ll of the beam 3. The concrete material forming the two 11 (which flanges are advantageously stepped in conformity with the stepped end portions of the two beams) is arranged to retain coupling cables 13 designed to operate in traction. The opposite end portions 13A and 13B of each cable (like the precompression cables) are anchored on the inner surfaces of the respective flanges 9 and 11. Before the cables 13 are tensioned, a hardenable mass, for example concrete or an epoxy resin is injected into the gap between the adjacent heads'of the two beams 1 and 3 to form a shim 15. This shim 15 is, after it has been allowed to harden, subjected to compression by tensioning the cables 13. This also results in the material of the flanges 9 and 1 1 being subjected to compression. The axial thickness of the flanges 9 and 11 and the anchoring of the end portions 13A of the coupling cables 13 and the end portions 5A and 7A of the precompression cables 5 and 7 are such that they produce a compression effect on the material between said anchorings, as indicated by the double arrow f of FIG. 4. In this way the material of the flanges 9 will be subjected to substantially only compressive stresses which act barycentrically to reduce hyperstatic or redundant reactions.

In order to decrease the number of the coupling cables 13 and to maintain the hardened mixture 15 under a relatively high compressive stress, the cross-sectional area of the hardened mixture 15 can be reduced to that designated in 15X in FIG. 4. The mixture here occupies a cross-sectional area equivalent to that of the adjacent beam beyond the flanges. This reduction in the crosssectional area enables a good efficiency for the flexure actions to be obtained while using only a relatively small number of coupling cables 13. These cables then can be protected by putty injected into the residual space 15Y (see FIG. 4) after the beams have been coupled and placed under stress.

FIGS. 5 and 6 show a viaduct structure having two contiguous supporting posts or piers 21 and 23 and a beam 25 partially supported by the pier 21.

As shown in FIG. 5 a prefabricated beam 27 is about to be laid onto the pier 23 with its end portion 27A about to rest on the end portion 25A of the beam 25. Once the two end portions 25A, 27A are brought into contact they are axially coupled in the hereinbefore described manner either immediately after the beam 27 is in position as shown in FIG. 6 or, and advantageously, after a delay which allows the complete relaxation of the steel of the precompression cables and the shrinkage and fluage of the concrete to take place.

In another viaduct structure shown in FIGS. 7 and 8, two adjacent piers 31 and 33 each carry a beam 35. The two beams 35 are arranged to be linked by beam 37. The beam 35 is designed so as to take predommantly negative moments, while the beam 37 is designed so as to take predominantly positive moments, the precompression cables being correspondingly arranged between adjacent end portions of the beams.

In the construction of the viaduct after the beam 37X which extends between the beam 35X in the pier 31 and its adjacent beam on the preceding pier (not shown) has to be located in position (by a procedure to be described for the subsequent beam), the beam 35Y is laid in a balanced condition on the pier 33. The beam is temporarily secured to the pier by a tie-rod 39. Then the beam 37Y is launched into position with one end portion 37A engaging the end portion 35A of the beam 35Y, and with its other end portion 378 engaging the end portion 358 of the beam 35X. After the launch, the beams 37Y and 35Y are coupled by coupling cables extending through the flanges of the beams. Thereafter the fluage of the concrete is allowed to settle and shrink before the coupling cables are tensioned to place the concrete under stress. The subsequent spans are formed in the same manner.

In FIG. 9 shows a section through a modified junction between two beams which allows a temporary seal between the two beams to be readily demolished, and replaced by a more permanent seal after the structure has been allowed to settle and the stresses reach a state of equilibrium.

As shown in FIG. 9, the adjacent end faces 41 of the two beams are inclined with respect to the vertical so as to define a gap which diverges with increasing distance from the common longitudinal axis of the beams. Spacers 43 of a detachable material (such as metal sheets, layers of synthetic resin, or artificial rubber and neoprene) are mounted on each end face 41 and a mass 45 is cast in the gaps between the spacers 43 to form a temporary seal between the beams. When the mass has hardened, it is placed under compression by tensioning the coupling cables 47 which extend through the adjacent flanges of the two beams. In this manner, the structure is made continuous. After a delay during which settlement has had time to take place, the coupling cables are loosened and the sealing 45 is removed. This is readily accomplished because of the presence of the spacers 43 and because the sealing mass is wedge-shaped, the mass can be removed in complete blocks with the aid of jacks or the like, or it can be broken in to fragments and removed fragment by fragment. A fresh hardenable mass is then injected between the beams.

In the modified junction between two beams shown in FIG. 10, the concrete mass is formed with the aid of a mold of plastic or other material which has been lowered into the gap between adjacent end faces 51 of two beams. The mold has two flanges which are arranged to engage the end faces 51 to form gaps between the side walls of the mold and the end faces 51. Concrete is thereupon cast both into the gaps between the walls of the mold and the end faces 51 to form blocks 55 and is also cast into the mold 53 itself to form an additional block 57. After sufficient time has been allowed for settling, the coupling cables 59 are loosened and the mold 53 together with the block 57 are removed to leave the blocks 55 in position. The mold 53 can thereafter be demolished. Thereafter the remaining gap between the beams is sealed in a more permanent manner.

In this manner it is possible both to assure the immediate continuity of the launched structure and to subse quently relieve the overstresses produced by casting the temporary concrete blocks before the complete structure has had time to settle.

The temporary sealing such as the ones denoted by 45 or 57 respectively in FIGS. 9 and 10 can advantageously be provided in the zone 61 or the zone 63 of the beam as indicated in FIG. 11.

An advantage of providing a temporary seal between beams is that the resulting continuous structure formed can be used almost straight away to carry new beams to be added to the structure into their required positions. This simplifies and speeds constructional operations since the launching bridge need not be made to traverse all the piers in order to pick up fresh beams from one end of the structure but can remain in a position where it is required, that is, at the end of the thus far completed structure.

In the construction of a continuous beam structure as indicated in FIG. 12, lifting equipment 65 for lifting successive beams into position has one leg mounted on the over-hang portion 61X of the completed length of the continuous beam 61 and its other leg mounted on a subsequent pier 67. Prefabricated beams 69 and 71 are conveyed along the completed length of the continuous beam 61 until they reach the equipment 65, whereupon the beam 69 is raised by the equipment and laid onto the pier 67 as indicated by broken lines 69X. Thereafter the beam 71 is raised by the equipment and laid between the beam 69 and the over-hang 61X.

The two beams 69 and 71 are then coupled by coupling cables as is the beam 71 with the over-hand portion 61X. Thereafter temporary casings are made at the beam junctions.

It will be appreciated that because the temporary casting is readily removable (which casting provides an initial continuity of the beam structure with the associated advantages) the resultant stresses resulting from settlements of the bonds, fluage of the concrete and relaxation of the'steel cables can be readily relieved.

This process of constructing continuous beam structures is particularly advantageous where the continuous beam structure has to follow a curved path and also for bridging spans in excess of 30 to 40 linear. meters and up to linear meters.

I claim:

1. A method of erecting a continuous beam structure, comprising the steps of placing at least two beams in end to end relationship,

securing the adjacent end portions'of the two beams together with reinforcing means,

injecting a hardenable mass between the adjacent end portions of the two beams, and

tensioning the reinforcing means to place the hardened mass under a compressive stress.

2. A method according to claim 1, wherein the mass comprises concrete.

3. A method according to claim 1, wherein the mass comprises an epoxy resin.

4. A method according to claim 1, wherein the step of tensioning the beams is delayed until after the interconnected beams have been allowed to relax and the stresses therein reach a state of equilibrium.

5. A method according to claim 1, wherein each beam is positioned so that it is supported in two spaced locations, in one of which it is supported by an adjacent beam of the continuous beam structure and in the other of which is supported on a pier.

6. A method according to claim 1, wherein each alternate beam of the continuous beam structure is made to rest on a pier with an intervening beam of the structure made to rest on the two adjacent alternate beams, each said alternate beam being arranged to withstand negative moments and each said intervening beam being arranged to withstand positive moments.

7. A method according to claim 6, including the step of temporarily securing each said alternate beam to its corresponding pier until the alternate beam supports intervening beams on both sides.

8. A method according to claim 6, wherein during the erection of the continuous beam structure, beams to be coupled to the end of the incomplete structure are transported by way of the already completed structure.

9. A method according to claim 1, wherein the step of injecting a hardenable mass is preceded by the step of placing detachable components between adjacent ends of the beams the step of injecting a temporary hardenable mass between the beams, the step of loosening the reinforcing means, and removing the detachable components together with the temporary hardened mass from between the beams after a delay during which the interconnected beams have been allowed to relax and the stresses therein reach a state of equilibrium. 10. A method according to claim 9, wherein each detachable component comprises a mold defining a central volume and when placed between the end portions of two adjacent beams forms a further two lateral volumes with the end portion, the step of injecting the temporary hardenable mass between adjacent beams including the step of filling all three volumes with the temporary hardenable mass. 

1. A method of erecting a continuous beam structure, comprising the steps of placing at least two beams in end to end relationship, securing the adjacent end portions of the two beams together with reinforcing means, injecting a hardenable mass between the adjacent end portions of the two beams, and tensioning the reinforcing means to place the hardened mass under a compressive stress.
 2. A method according to claim 1, wherein the mass comprises concrete.
 3. A method according to claim 1, wherein the mass comprises an epoxy resin.
 4. A method according to claim 1, wherein the step of tensioning the beams is delayed until after the inter-connected beams have been allowed to relax and the stresses therein reach a state of equilibrium.
 5. A method according to claim 1, wherein each beam is positioned so that it is supported in two spaced locations, in one of which it is supported by an adjacent beam of the continuous beam structure and in the other of which is supported on a pier.
 6. A method according to claim 1, wherein each alternate beam of the continuous beam structure is made to rest on a pier with an intervening beam of the structure made to rest on the two adjacent alternate beams, each said alternate beam being arranged to withstand negative moments and each said intervening beam being arranged to withstand positive moments.
 7. A method according to claim 6, including the step of temporarily securing each said alternate beam to its corresponding pier until the alternate beam supports intervening beams on both sides.
 8. A method according to claim 6, wherein during the erection of the continuous beam structure, beams to be coupled to the end of the incomplete structure are transported by way of the already completed structure.
 9. A method according to claim 1, wherein the step of injecting a hardenable mass is preceded by the step of placing detachable components between adjacent ends of the beams the step of injecting a temporary hardenable mass between the beams, the step of loosening the reinforcing means, and removing the detachable components together with the temporary hardened mass from between the beams after a delay during which the inter-connected beams have been allowed to relax and the stresses therein reach a state of equilibrium.
 10. A method according to claim 9, wherein each detachable component comprises a mold defining a central volume and when placed between the end portions of two adjacent beams forms a further two lateral volumes with the end portion, the step of injecting the temporary hardenable mass between adjacent beams including the step of filling all three volumes with the temporary hardenable mass. 